1. Field of the Invention
The present invention relates to a drawing apparatus and a method of manufacturing an article.
2. Description of the Related Art
A drawing apparatus which performs drawing on a substrate with charged particle beams requires a large angle of view of a charged particle optical system (illumination optical system) in order to increase the throughput. However, a large angle of view of the charged particle optical system increases aberrations of the charged particle optical system, and there is a fear of degradation of telecentricity or generation of illuminance nonuniformity.
To solve this, Japanese Patent Laid-Open No. 2009-32691 discloses a technique of improving telecentricity by individually deflecting a plurality of charged particle beams split by an aperture. Japanese Patent Laid-Open No. 2010-41055 discloses a technique of correcting illuminance nonuniformity by using apertures for splitting a charged particle beam, the sizes of which are different depending on the position.
The apertures whose sizes are different depending on the position can correct assumed systematic illuminance nonuniformity. However, when illuminance nonuniformity deviates from the assumed value or an unsystematic (local) component is large, it is difficult to correct the illuminance nonuniformity. Every time illuminance nonuniformity deviates from the assumed value, a new aperture corresponding to the illuminance nonuniformity may be manufactured and used in the drawing apparatus (that is, the aperture is replaced). However, this prolongs the downtime of the drawing apparatus, decreases the throughput, and increases the cost.